Below slab gas removal and sump system

ABSTRACT

A radon removal system includes a slab forming part of a foundation of a building, a barrier layer laid under the slab, the barrier layer being vertically gas impermeable and horizontally gas permeable. A gas inlet in the sealed system provides a fluid connection for gas flowing from the barrier layer through a sealed system (for example a sump body with water inlet, sump pump and water outlet) to a gas outlet. A negative pressure generated by the sealed system brings gas from the barrier layer into the sealed system through the gas inlet and out of the sealed system through the gas outlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119 of Canadian non-provisional application serial no. 2898976 filed Jul. 30, 2015, and Canadian non-provisional application serial no. 2894037 filed Jun. 8, 2015.

TECHNICAL FIELD

Building construction.

BACKGROUND

Radon gas has been identified as a hazardous material that occurs naturally within the ground and that may enter buildings through their foundations due to buildup of radon gas pressure. Some building codes, such as the National Building Code of Canada, require that in new building construction measures be taken to prevent radon from entering the envelope of a building. When constructing a new home, builders may use a range of approaches, including installing an air barrier under the foundation slab and an air tight cover for the sump pit to prevent the entry of radon, and a rough-in for a possible future subfloor depressurization system, should radon problems emerge. To reduce radon gas pressure under a foundation slab, a published recommendation suggests a vent extending upward through the centre of the slab from below to above the slab, such a vent being connected to a pipe that extends laterally below the slab, or a pipe that extends from the centre of the slab underneath the slab to a vent elsewhere. In each case, radon gas pressure is thereby reduced under the slab.

SUMMARY

In an embodiment, there is provided a radon removal system, comprising a slab forming part of a foundation of a building; a barrier layer laid under the slab, the barrier layer being vertically gas impermeable and horizontally gas permeable; a sealed system having a gas inlet providing a fluid connection to the sealed system for the gas collecting under the barrier layer and a gas outlet for removing gas from the sealed system, the sealed system generating a negative pressure for drawing gas from under the barrier layer through the gas inlet to the gas outlet.

In an embodiment, there is provided a radon removal system comprising a vertically gas impermeable and horizontally gas permeable barrier layer having a fluid connection through a gas inlet into a sealed system to a vent, the sealed system having a blower for generating a negative pressure in the gas inlet, the sealed system comprising a sump body having a water inlet and a sump pump connected to a water outlet.

There is also disclosed a radon removal system comprising a slab forming part of a foundation of a building, a sealed system having a gas inlet providing a fluid connection to the sealed system for gas collecting under the foundation and a gas outlet for removing gas from the sealed system, the sealed system generating a negative pressure for drawing gas from under the foundation through the gas inlet to the gas outlet.

In various embodiments, there may be included any one or more of the following features: the gas inlet comprises perforations in the sealed system; the gas inlet comprises a pipe which extends under the barrier layer or foundation; the pipe is a perforated pipe; the pipe extends under the foundation to a central area of the foundation; the gas outlet is a vent; the sealed system comprises a sump body or container; the sump body comprises a water inlet, sump pump and water outlet; the sump body has an interior and window for allowing viewing of the interior of the sump body; the sump body comprises a neck embedded in the slab with a gasket around the neck between the neck and the slab; the pipe comprises weeping tile; the pipe comprises hard plastic; a blower in the sealed system generates negative pressure in the sealed system for drawing gas from under the barrier layer or foundation through the gas inlet to the gas outlet; the vent comprises a vent pipe extending from the sealed system to outside the building and the blower is within the vent pipe; the sealed system comprises a container with inlets for the flow of gas into the container; the container comprises a water inlet, sump pump and water outlet, the barrier layer comprises a membrane, which may be dimpled and include a fabric underlayer.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which:

FIG. 1 is a section view of an embodiment of a radon removal system showing a sump body with pump and vent system, wherein the sump body provides a sealed unit for evacuating radon from underneath a slab and venting the gas to atmosphere;

FIG. 2 is a top view of the sump body of FIG. 1 with the ground broken away to show an inlet perforated pipe for drawing radon gas from under the foundation, as well as an inlet water pipe for drawing water into the sump body from the weeping tile normally found around a foundation, and each inlet pipe connecting to the sump body;

FIG. 3 is a section view of the embodiment of FIG. 1 taken along line A-A, showing a pipe laid below a membrane for collecting gas;

FIG. 4 shows a barrier layer formed of a dimpled membrane with fabric underlayer, the layers are shown slightly separated for clarity but in practice would be in contact.

DETAILED DESCRIPTION

Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims. In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.

As shown in FIG. 1, a radon removal system 10 is provided and works in conjunction with a slab 12 forming part of a foundation of a building that includes a footing 14 and wall 16. The slab 12, footing 14 and wall 16 are all conventional and may have various configurations depending on the building structure. In an embodiment, a barrier layer or membrane 18 is laid under the slab 12 to the edges of the slab 12, or such other location as permitted by local building regulations. The barrier layer 18 is vertically gas impermeable, preferably with an impermeable upper layer, and provides a barrier to gas thereby redirecting gas flow under the slab 12. The barrier layer may comprise a membrane with a permeable under layer formed for example of dimples 21 or other permeable structure that is part of the membrane to allow horizontal movement of gas under the membrane, and thus the barrier layer is horizontally gas permeable to collect gas in and beneath the barrier layer 18. The barrier layer 18 may have multiple layers which are each permeable or impermeable. To prevent the dimples 21 becoming embedded in a layer, for example gravel 36, under barrier layer 18, the barrier layer 18 may be underlain by a gas permeable cloth or fabric 19. The barrier layer 18 provides an air gap between the slab 12 and materials under the barrier layer 18. In another embodiment, the barrier layer 18 may comprise an impermeable sheet or membrane with permeable particulate under the impermeable sheet to provide horizontal movement of gas.

A container or sealed system 20 is provided under the slab 12 or in another suitable location. For example, the sealed container 20 may be provided outside of the foundation or within the building. The container 20 is sealed between any inlet for gas into the system through to the blower so that gas is evacuated from the container 20 through a vent such as vent 26. A gas inlet 22 in the sealed system 20 provides access to the sealed system 20 for gas which collects under the barrier layer 18. Thus, the barrier layer 18 is fluidly connected to the sealed system 20 by the gas inlet 22. The sealed system 20 generates a negative pressure from the gas inlet 22 to a gas outlet 24 in the sealed system 20. For example, a vent or vent line 26 may be provided for the sealed container 20 that extends to the roof of the building or other suitable location for the disposal of radon gas. A blower or fan 28 may be provided inline in the vent line 26 to provide a negative pressure on the interior of the container 20. Operation of the blower or fan 28 draws gas collecting outside the sealed container under and through the membrane into the sealed container 20 and up into the vent 26. Depending on the strength of the blower 28, the container 20 and the related system components need only be sufficiently sealed to allow the system to function, and this is what is meant by sealed. A functioning system draws gas from under the slab and vents to a safe place, such as to the exterior of the building from a roof of the building. The blower or fan 28 may be any of various commercially available fans.

The gas inlet 22 thus provides a fluid connection to the sealed system 20 for gas collecting under the barrier layer 18 and the gas outlet 24 allows gas to be removed from the sealed system 20, the sealed system 20 generating a negative pressure for drawing gas from under the membrane 18 through the gas inlet 22 to the gas outlet 24. The gas inlet 22 may be for example perforations 30 in the sealed system 20 or a pipe 32 such as a perforated PVC pipe extending under the membrane 18 or both. The container or sealed system 20 may have multiple gas inlets 22 for gas collecting under the barrier layer 18. The multiple gas inlets may comprise for example multiple pipes 32 extending under the barrier layer 18 or a single pipe 32, with or without branches, or comprise perforations. In some embodiments, perforations in pipe 32 or container 20 allow gas collecting under the barrier layer 18 to flow into the container 20. The pipe 32 is connected via a sealed connection to the container 20. Radon gas may thus be drawn by negative pressure through the pipe 32 or perforations 30 to the interior of the sealed container 20.

The barrier layer 18 is thus connected to the vent 26 through a sealed system to the blower 28 for generating a negative pressure through pipe 32 for drawing gas from under the membrane 18 through the pipe 32 to the vent 26. The vent 26 may be a pipe such as a PVC pipe. Radon gas may be collected in the perforated pipe 32 and be pulled by the negative pressure from the blower 28 through the sealed container 20 to the vent 26, to release the radon gas outside the building. The radon gas may be released through the roof of the building.

The perforated pipe 32 may extend under the foundation 12 to a central area of the foundation 12 for the collection of radon gas. Permeable material 34, for example washed gravel 36 of a type and thickness depending on local code requirements, may underlay the slab 12 and provide a path for radon gas to reach the pipe 32, as shown in FIG. 3. Permeable material may also be for example road crush 38 such as compacted road crush, which may form a separate layer from other permeable materials 34. Permeable material 34 may also surround the sealed container 20 and lie beneath the entire floor of the building. The perforated pipe 32 may comprise for example weeping tile or hard plastic, such as PVC. Hard here means sufficiently hard that in normal use the plastic retains its shape, for example when the pipe is made of PVC. In another embodiment, the pipe 32 is not perforated, but is sealed and extends to underneath the center of the slab. A screen 40 may be provided in the pipe 32 at the gas inlet 22. The screen may for example prevent particulate matter from entering the sealed container 20. The screen may be a non-corroding screen.

The container or sealed system 20 may comprise a sump body 42, provided under or above the slab 12. The sump body 42 may comprise a water inlet 44 connected to a suitable fitting on the sump body, sump pump 46 and water outlet 48. The water inlet 44 may be for example a tee pipe 50 which leads out to weeping tile 52, or other water collection material permitted by local code requirements. Water collecting around the foundation flows into weeping tile 52, and then flows into the tee 50 and into the container 20, where it collects on the bottom of the sump body 42. The water outlet 48 may be a pipe which extends from the sump pump 46 through the floor of the building. Depending on the local code requirements, the water outlet 48 may dispose of water outside onto or into ground surrounding the building or into a municipal water disposal system. The container 20 may have a raised bottom 54. The sump body 42 may operate in the normal manner of a sump, such that the pump 46 periodically turns on to pump water out of the sump body 42, for example when a high water level is reached. Conventional sump pumps may be used for the pump.

As shown in FIG. 2, the sump body 42 may be provided with a viewing window or access cover 56. For example, the viewing window 56 may provide a way to visually assess the interior 60 of the sump body 42 without removing the viewing window 56. The vent 26 for releasing radon gas may extend from the sealed system 20, and similarly the water outlet 48 for the sump body 42 may extend from the sealed system 20, in close proximity to the viewing window 56. An electrical connection 62 for the pump 46 and blower 28 may also extend from the sealed system 20 in close proximity to the viewing window 56. The pump 46 and blower 28 may be connected via the electrical connection 62 to a power source (not shown) for example the conventional electrical supply for the building through a conventional plug in. Level controls for the sump body 42 may also be provided through the electrical connection 62. The fan 28 may be allowed to run continuously.

As shown in FIG. 1, when the container 20, here sump body 42, is provided underneath the slab 12, the container 20 or sump body 42 may comprise a neck 64 embedded in concrete, such as for example the floor of the building, with a gasket 66 around the neck 64 and the concrete to maintain a seal between the sump body 42 and slab 12 and prevent gas from entering the building around the container 20. If the slab 12 is made of concrete, the neck 64 may be embedded in the slab 12. The gasket 66 may be made of rubber. Various sizes of components may be used. The lid or access cover 56 may also be provided with a gasket or other sealing element between the lid or access cover 56 and the sump body to be liquid and air tight with reusable fasteners 68. The lid or access cover 56 may be removed in order to access the interior 60 through the access opening 58 of the container 20.

In some embodiments, the sump body 42 may have a number of conventional features, including for example a high level alarm which may be for example set at 22″ above the bottom of the sump body, a second pump, a float switch for each pump in which one of the switches may be for example set at 18″ above the bottom of the sump, and a low level float which may for example pump off 6″ above the bottom of the sump.

In some embodiments, the slab may be 4″ of concrete, washed rock may be 100 mm washed rock, the pipe 32 may be 4″ pipe, the tee 50 may be 4″ pipe, and the vent 26 may be made for example from 3″ or 4″ pipe, such as PVC plastic. The washed rock may also be crushed. The sump body 42 may be of varying depths depending on the site, such as for example 32″ or 72″. The barrier layer 18 may include layers made from HDPE, or heatbonded polypropylene geotextile, and may for example be a DELTA® product such as DELTA®-DRAIN or DELTA®-MS UNDERSLAB. The barrier layer 18 may comprise geotextile with a permeable underlayer.

In an embodiment, the radon removal system may reduce and maintain radon concentration to a level below 100 Bq/cu m after activation of the mitigation systems or as otherwise required. Radon removal system piping should be routed so as not to interfere with the daily operations and functions of the building occupants. Radon removal system discharge points should be as per local code requirements and may be configured to prevent foreign objects from entering the outlet. Radon collecting pipes may slope down to the sump.

In an embodiment, a system failure warning monitor may provide a means to detect and announce a radon removal system failure. A system failure may be a system blockage, for example by foreign debris, a mechanical failure, for example of a fan or other mechanical failure, or a system leakage, for example a pipe breakage or crack. The system failure warning monitor may include an audio or visual annunciator device to indicate system failure.

In an embodiment, the radon removal system components may conform to the following standards, depending on jurisdiction: the poly(vinyl chloride) (PVC) Piping: ASTM D2665, schedule 40; in-line tubular centrifugal fans: AMCA 210 and UL listed; Sealants: ASTM C920, polyurethane, Type S, Grade P for horizontal application, Grade NS for vertical application, Class 25, Use T. The below-slab membrane should be a minimum 10-20 mils thick and may have at least the following tensile properties (ASTM D-751): grab tensile warp (lbs.) 165, grab tensile weft (lbs.) 145 and may have the following tear properties (ASTM D-751): tongue tear warp (lbs.) 40, tongue tear weft (lbs.) 42. The membrane may have a coefficient of friction of 0.72 (ASTM D5321), confirmed micro-organism resistance and heat aging testing (ASTM D4068-88), confirmed environmental stress cracking testing (ASTM D169378). A soil-gas retarder membrane for use in a crawl space should be a minimum 40-60 mils thick.

In an embodiment a gas permeable venting layer below the membrane may be a 100-150 mm minimum thick layer of 19-25 mm permeable material 34, for example washed clear granular material. The membrane may be a high compressive strength copolymer polypropylene drainage board, impact resistance, tear resistance and stress cracking resistance suitable for horizontal installations. The membrane may have a dimple height of 10 mm or more, compressive strength of 527 kN/m2, geotextile tensile grab strength of 445N, Mullen burst 1446 kPa, water flow 5703 l/min/m2. The dimples may provide horizontal flow beneath the membrane upper impermeable layer.

In an embodiment the pipe may be roughed-in radon sub-slab depressurization suction pipes and should be placed into the gas permeable venting layer having a minimum thickness of 100-150 mm. The pipe may be of non-perforated or perforated—SDR 21—smooth walled 100-150 mm (inside) diameter rigid pipe of PVC or high density polyethylene. The pipe may be sloped to the gas inlet in the container.

In an embodiment, a vent or vent line may be used for each container location and extend from within the container to the exterior through the roof.

In an embodiment, the fan 28 may be an energy efficient, sealed seam, ETL listed, radon mitigation fan with a thermally protected motor. The fan 28 should be specifically suited for radon mitigation. The fan may be 150 mm in diameter, 92-129 Watts, 2.3″ wc Max SP, with performance of 176 CFM at 1″ SP. For example, the fan may be a RadonAway® RP 265 series. In further embodiments the fan may have a variable speed drive, a fan operation failure sensing device, weather tight disconnect enclosure.

In an embodiment the perforated pipes may be installed in and surrounded completely by washed rock. The maximum size of the perforations in the pipe should be 50% smaller than smallest diameter of the rock fill designation.

In an embodiment the membrane may be overlapped creating a seam and the membrane seams may sealed with sealant at all overlap junctions and transitions with a minimum of 300 mm overlap. All membrane seams may be thermally or chemically sealed. The membrane is to be terminated with an upturn at the perimeter grade beams, footings and strip footings and terminate between the beam or footing and finished floor slab. The membrane may terminate midway through the floor slab and be sealed to the beam or footing on 300 mm centers. A sealant may be applied to any junction between membrane to footing, beam or floor slab. Gas tight seals should be provided around the surfaces of all vertical penetrations. Sealants and construction tape may be used as required to provide a continuous seal between the membrane and any pipe, conduit or other item that penetrates the floor slab. Sealant may be applied to all penetration junctions on the top side of the finished floor slab, once floor slab has cured. Upturns may be mechanically fastened, membrane self-adhered, sealant sealed and/or construction taped to the component penetrating the floor slab. 

1. A radon removal system, comprising: a slab forming part of a foundation of a building; a barrier layer laid under the slab, the barrier layer being vertically gas impermeable and horizontally gas permeable; a sealed system having a gas inlet providing a fluid connection to the sealed system for the gas collecting under the barrier layer and a gas outlet for removing gas from the sealed system, the sealed system generating a negative pressure for drawing gas from under the barrier layer through the gas inlet to the gas outlet.
 2. The radon removal system of claim 1 in which the gas inlet comprises perforations in the sealed system.
 3. The radon removal system of claim 1 in which the gas inlet comprises a pipe that extends under the barrier layer.
 4. The radon removal system of claim 3 in which the pipe is a perforated pipe that extends under the foundation to a central area of the foundation. 5-6. (canceled)
 7. The radon removal system of claim 1 in which the sealed system comprises a sump body and the sump body comprises a water inlet, sump pump and water outlet.
 8. The radon removal system of claim 7 in which the sump body has an interior and window for allowing viewing of the interior of the sump body.
 9. The radon removal system of claim 7 in which the sump body comprises a neck embedded in the slab with a gasket around the neck between the neck and the slab. 10-11. (canceled)
 12. The radon removal system of claim 1 in which a blower in the sealed system is provided to generate, in operation, a generates negative pressure in the sealed system for drawing gas from under the barrier layer through the gas inlet to the gas outlet.
 13. The radon removal system of claim 1 in which the gas outlet comprises a vent pipe extending from the sealed system to outside the building and the blower is within the vent pipe.
 14. The radon removal system of claim 1 in which the barrier layer comprises a membrane.
 15. The radon removal system of claim 14 in which the membrane comprises a dimpled underlayer.
 16. The radon removal system of claim 15 further comprising a fabric layer beneath the dimpled underlayer. 17-25. (canceled)
 26. A radon removal system, comprising: a slab forming part of a foundation of a building; a pipe extending under the slab; the pipe being connected to a vent through a sump defined by a container; and the container having a neck embedded in the slab, the neck extending vertically with a gasket around the neck between the neck and the slab.
 27. The radon removal system of claim 26 in which the vent has a blower for generating a negative pressure in the pipe
 28. The radon removal system of claim 27 in which the vent comprises a vent pipe extending from the sump to outside the building and the blower is within the vent pipe.
 29. The radon removal system of claim 26 in which the pipe is perforated pipe.
 30. The radon removal system of claim 26 in which the pipe extends under the foundation to a central area of the foundation.
 31. The radon removal system of claim 26 in which the sump comprises a water inlet, sump pump and water outlet.
 32. The radon removal system of claim 26 in which the sump has an interior and window for allowing viewing of the interior of the sump.
 33. The radon removal system of claim 26 in which the pipe comprises weeping tile.
 34. The radon removal system of claim 26 in which the pipe comprises hard plastic. 